In this kind of inductive load driving device, a load including an inductance component, such as a motor or a lamp, is driven by on/off of a semiconductor switch element, and a clamping circuit that clamps counter-electromotive force to a predetermined voltage is provided such that, when the semiconductor switch element transfers to an off-state from an on-state, the semiconductor switch element is prevented from being broken by direct supply of the counter-electromotive force due to flyback energy accumulated in the load to the semiconductor switch element.
In the conventional example described in JP 2004-247877 A, an output MOSFET is connected between a ground and the other end side of an inductive load whose one end is connected to a power source, and, as an arc-extinguishing circuit, a dynamic clamping circuit in which four zener diodes whose connection stages can be varied by a plurality of switches, and a sneak current preventing diode are connected in series is connected between a terminal on the load side (drain) and a gate of the output MOSFET. By varying the connection stages of the zener diodes of the dynamic clamping circuit, an arc-extinguishing voltage is changed without changing hardware.
In addition, in the conventional example described in JP 2009-232499 A, an electric motor drive control device for a vehicle, which includes: an electric motor drive element including a first switching unit between a power source and an electric motor, which switches power feeding to the electric motor and stopping and is composed of a MOSFET, and a switching circuit which is arranged between a drain and a gate of the first switching unit and can switch a clamp voltage between a first clamp voltage and a second clamp voltage having a value larger than the first clamp voltage; and a clamp element which is connected in parallel to the electric motor drive element and clamps to a third clamp voltage having a value between the first clamp voltage and the second clamp voltage is disclosed.